Need cooling system help please

It's a bit difficult to parse all the information you have there in your wall of text. One point though, if half of your 54k is in low gear you effectively have 100k on the vehicle. Though my 2009 rubicon just rolled over 200k, these are long lasting engines, with quirks.

So is the heater working? It is almost impossible to burp the heater core on flat ground for these. The front has needed to be elevated when I've done it. The overflow will only work if the main system is pretty close to the top, so you may have air in there and never gotten it out.

From factory there isn't a gasket around were you put the thermostat. I added a crush one here and my system started working
better. I was getting a very slow leak that would drip onto the block and evaporate. Took a couple years to finally find where my coolant was going. I think it's the reason that these models can have a coolant smell when you walk by the front after shutting off.

Have you flushed the heater core? What version of coolant have you topped it off with? Did you use the right stuff? I stopped getting anything but universal because I don't want to play the jelly in my coolant system game.

Either the stick did more damage than you think, or perhaps an ECU reset could make the system relearn when to turn on the fan. Though the system not getting hot enough for the fan... thermostat.. just sayin'. I've never had a fan problem, just an occasional over achieving fan when my coolant was low before I finally found my problem.

Have you checked the fan relay? Right behind the driver side headlight?
Seen a lot of guys replace the fan, temp sensor and even fuses. Turns out there is a relay mounted between the driver side headlight and the coolant reservoir.

Creston said:

I can command the fan on with the AC and by my computer so I think all wiring and such is ok

Click to expand...

I understand. But I've read the relay is on a separate circuit and read where the fan continues to run after the engine is off or the fan only operates when the AC is on, etc.

I believe the fan relay takes input from the temp sensor as well as the AC and that part of the relay can go bad, such as just the AC side or the cooling fan side.

BLACKJKU said:

But if that part of the relay was bad then he wouldn't be able to command it on the way he is.

Click to expand...

Right, but he says:

"The system is getting hot enough. The ect sensor is reading correctly. The old one was too but was jumpy. I can even run the ect sensor up to 220 and the fan doesn't come on. Thermostat is 195 so id assume fan is around that. I can watch the computer output with my scan tool. It's not telling the fan to come on unless I over ride it or turn on the AC, which forces the fan on, on most vehicles (if not all) to cool the condenser. Fan works fine if manually turned on or by the AC"

So, if you open the relay, there are 5 leads. The temp sensor and the AC are included in those leads coming from different places. So, while the AC may be working fine, the temp sensor may be working by sending a signal to the relay to turn on the fan, but if the relay is bad, the fan doesn't run.

I'm not sure how to "override" the relay even if you run up the ECT temp to 220 and the fan isn't coming on. If you're able to override from a Jscan or similar, how do you know which part of the relay is being controlled by that override?

Does that make sense?

https://realjenius.com/2018/06/28/pentastar_radiator_fan/

The 2012 and up Jeep JK wrangler fan on the 3.6L Pentastar has a few key characteristics:

• It is an Outrunner motor design. This doesn’t have much bearing on diagnosing problems, but it’s a key difference from the more traditional fan designs in the earlier Jeep JKs
• The fan is a 3 wire design, which you can see if you detach the harness. The three wires are:
  • Heavy gauge power directly from the battery
  • Heavy gauge ground wire which terminates behind the power steering fluid reservoir
  • A small gauge wire that is the “pulse width modulated duty cycle signal” from the circuitry in the TIPM (aka smart fuse box)

Now, typically, a system like the old JK setup will have relays to do “high amperage” power switching. For example, if a fan needs 60 amps to run on high speed, the high speed relay acts as a large switch which, when enabled, sends the high amperage power to the fan to run. As soon as the power reaches the fan, it kicks on. However, given the description above you’ll notice the only voltage going to the fan (other than the piddly PWM wire) is coming directly from the battery; no relays, and therefore no external control.


What that means is all of the circuitry for enabling the fan and controlling the fan speed is contained inside the fan assembly itself. The fan expects to get power from the battery at all times (so it can run even when the car is off), and translates the PWM duty cycle signal from the computer in the TIPM into a variable speed for the fan itself.


Consequently, the fan for a 2011 and prior JK Jeep is around $65 to $200 dollars, and there is a ton of aftermarket competition. However, the “fan assembly” for the Pentastar is pretty much only made by Mopar (Part 68143894AB), and it costs $400 on a good day.


Part of the reason for a lack of an aftermarket is the complexity of having to reproduce a competitively priced setup that can do the same thing while keeping the factory computer from throwing codes. To work with the factory setup, any fan assembly has to:

• Read the pulses on the signal wire correctly (or ignore them and be less efficient or require an alternate signal source)
• Translate those into variable fan speeds (or ignore them… see above)
• Provide the correct resistance back to the TIPM computer so it will not throw an OBDII code

Aside from this complexity, another major reason there isn’t much aftermarket is that the 3.6L fan itself is actually pretty good. The outrunner design makes it efficient and reliable, and based on others' testing, even in heavy off-roading setups the 3.6L fan is able to keep up just fine.


So, I knew that the fan wiring seemed deceptively simple. But what I also knew was that there are tons of parts under the hood that are labeled as belonging to the fan. Notably:

• The 60A fuse (J19) in the TIPM labeled “radiator fan”
• The Relay in the TIPM (K11) labeled “Radiator Fan Low”
• The dual relays over by the brake master cylinder labeled “Fan Relays” on the internet (Mopar Part 56055666AB)
• The lack of a P069X style code being thrown led me to believe this was a unique problem with only the “high” speed part of running the fan.

I checked and re-checked all of this in hopes of a cheap and easy fix. You can see some of my research notes here: P0480 - How to Diagnose 3.6 PWM Fan Issues


However, as it turns out, none of this is used for the radiator fan. As best as I can tell, some of this is leftovers from the old design, and some of this is likely used for other things (I suspect the fan relays are actually for the blower motor and AC system, though I don’t know for certain). I stared at this wiring diagram (found here thanks to BBB Industries), trying to figure out why the above components weren’t on it.

Why aren’t the components on it? Simple: they aren’t used!


Also, as far as I could tell, the only code the fan will ever throw on these newer jeeps is P0480, which is all encompassing to mean the TIPM asked the fan to turn on, and couldn’t detect that it did, or the engine overheated under a certain MPH and the computer doesn’t know why.


Assuming you are getting valid temperature readings from the engine temp sensors, the only components you have to worry about when diagnosing the 2012+ Pentastar 3.6L JK radiator fan not running are:

• The Fan assembly itself
• The TIPM itself (aka, the computer for most accessories in the car)
• The power lead from the battery
• The fusible link (S108) between the battery and the power lead
• The ground to location G904A (behind the power steering reservoir)

Unfortunately, testing the TIPM output requires a TIPM diagnostic tool (dealer equipment) or at least an oscilloscope so you can visualize the duty cycle square-wave coming from the PWM signal (even if you don’t know it’s right, seeing it would add confidence). It’s not something I was able to ever actually capture using my multimeter.

Also unfortunately, you cannot simply bench-test the fan. Believe me, I tried. If you jump the fan to power and ground and try to provide a direct 12V signal to the PWM lead, nothing will happen and you will think your fan is broken, when in actuality it may just be ignoring the signal because it is not a valid duty cycle.

So, inevitably you may have to go to the dealership for a diagnosis (or you may just blindly replace the fan and the TIPM for a cool $1000 in parts and a bunch of time in your own garage), however, before you do that, it’s worth checking everything else.

So, what was it in my case? Shockingly simple: The 10mm nut holding the fusible link to the battery had worked itself loose. It was still touching, but it was not a tight fitting. As a result, I was testing the power to the fan with a multimeter and getting a solid 12-14 volts, but the connection was not reliable enough to provide the high amperage demands of the fan, so the fan was not running, and the code was being thrown. If I had to play nostradamus, I’d guess that months ago when I installed my stereo I managed to back this nut off some (likely on accident) and didn’t notice. It just finally worked itself loose with enough bumps and jerks to make the fan unhappy.

If that isn’t your case, the other two likely causes:

1. The ground - if the ground is not stable and strong, you’ll get the same symptoms I experienced.
2. The fusible link - This is just a stretch of wire that serves as a fuse, and is inline between the battery and the main fan power wire. If it fails, you will know with a multimeter at the fan harness as you won’t be able to get a 12V signal at all (which does not have to be the case with loose fitting connections). Note however, if the fusible link is blown it could mean your fan is over-drawing current. The link exists to prevent the fan from pulling too much power. That typically happens with fans when the motor is overworked or possibly failing. If this is happening to you, and after replacing the fusible link it happens again, you are probably due for a fan replacement. A lot of forum posts talk about cleaning mud and debris out of the fan - certainly anything that inhibits the fan rotating should be cleaned out before throwing the whole assembly out.

Thankfully, both the TIPM and fan assembly are relatively easy to remove and replace based on my research. I nearly had the fan out of my Jeep in 15 minutes after removing the air box and some of the surrounding parts to verify the wiring (however, it turns out I didn’t need to). This article describes the TIPM replacement process – while I didn’t have mine completely out, I did have it unbolted from the Jeep and was able to see under the unit. It’s expensive, but not hard to swap out.